Lamp pinch seals

ABSTRACT

In an electric lamp having a pinch which hermetically seals the lamp envelope to thin foils forming part of lead-in conductors to the lamp filament, the central part of the pinch containing the foils is offset sideways slightly during pinch sealing, to prevent the inner parts of the conductors, which connect the filament to the foils, being deflected so that these parts extend into the interior of the envelope parallel to the central axis through the lamp.

United States Patent 11 1 Wolfe et a1.

[ LAMP PINCH SEALS [75] Inventors: Kenneth Roy Wolfe; Clive ArthurEvander Underwood, both of London, England [73] Assignee: ThornElectrical Industries Limited,

London, England [22] Filed: Apr. 4, 1973 [21] Appl. No.: 347,825

[30] Foreign Application Priority Data Apr. 14, 1972 United Kingdom .117392/72 [52] US. Cl. 240/41 BM; 313/220; 313/318 [51] Int. Cl. F2lm3/00 [58] Field oi Search 313/220, 318, 315; 240/41 BM [5 6] ReferencesCited UNITED STATES PATENTS 1,788,231 1/1931 Ceader et a1 240/41 BM UX2,749,527 6/1956 Gast 313/318 UX 3,262,001 7/1966 Rijckeart 313/318 X3,290,134 12/1966 Camarata i 29/520 X 3,315,216 4/1967 Krupp et a1.313/318 UX [451 May 20, 1975 Primary ExaminerFred L. Braun Attorney,Agent, or Firm-Dike, Bronstein, Roberts, Cushman & Pfund [57] ABSTRACTIn an electric lamp having a pinch which hermetically seals the lampenvelope to thin foils forming part of lead-in conductors to the lampfilament, the central part of the pinch containing the foils is offsetsideways slightly during pinch sealing, to prevent the inner parts ofthe conductors, which connect the filament to the foils, being deflectedso that these parts extend into the interior of the envelope parallel tothe central axis through the lamp.

9 Claims, 4 Drawing Figures LAMP vnvcn SEALS The present inventionrelates to improved lamp pinch seals suitable, inter alia, for precisionlamps such as pre-focus lamps.

When manufacturing precision lamps, internal components including, forexample, filaments, reflectors or shields, conductors and the like haveto be mounted with great accuracy within their envelopes. Unless this isdone, the lamps are unable to provide optimum performances wheninstalled in their associated optical equipment. Furthermore, in lampsof the tungstenhalogen type, it is essential to locate their filamentsexactly in relation to the quartz envelopes otherwise poor operatingcharacteristics and lives result.

Nowadays, it is common to pinch-seal lamp envelopes about theirconductors. The conductors frequently include molybdenum foils formingconductive paths between outer conductor wires and inner conductorwires, the latter extending into the bodies of the envelopes andsupporting the internal components of the lamps. Hermetic sealing-isachieved by pinching the envelope material against the foils. The foilsact as barriers preventing the envelope material, eg. quartz, fromflowing around these foils so that they remain central within theultimate seals. That is, equal thicknesses of quartz are found on eitherside of the foil in a finished seal.

The only practical way of affixing the conductor wires to a foil is toweld them to one of the faces of the foil.

Accordingly, the conductor wires are off-centre relative to theassociated foil, and during pinch sealing, the conductor wires aresubjected to bending forces. In the result, the internal components ofthe lamps are found to be somewhat displaced from their designedpositions. This phenomenon is discussed in greater detail hereinafter.Suffice it to say, here, that it has been extremely difficult, usingprevious pinch sealing techniques, to produce lamps with the desireddegree of precision.

According to the present invention, there is provided a lamp having anenvelope containing at least one filament and support means therefor,the support means including at least two inner conductors that areelectrically connected through separate conductive foils to externallyaccessible outer conductors, the envelope being pinch sealed to thefoils such that equal thicknesses of envelope material are in contactwith the opposite faces of each foil, and the seal portion within whicha foil is embedded being displaced laterally relative to the remainderof the seal so that each inner conductor extends into the envelope fromits associated foil in a direction parallel to a central longitudinalaxis through the lamp, the foils being displaced from this axis. Theinvention is applicable to both single and double-ended lamps, which canincorporate one or more envelope-to-conductor pinch seals as desired.The re sults of laterally displacing a seal portion within which a foilis embedded is that each pinch seal has a projection on one face and acorresponding depression in its other face. A lamp capping and mountingstructure can be fitted to each pinch seal, and'conveniently is soconstructed as to ensure that the lamp accurately focussed in a lightfitting designed therefor. A preferred embodiment is an automobileheadlamp bulb which is single ended and has two filaments and threeconductors, the

inner conductor elements, which may be in the form of wires, all lyingin a common plane in which the central longitudinal axis lies.

The invention further comprises a method of making a lamp, including thesteps of inserting into an envelope an assembly comprising a supportmeans bearing a filament and including lead-in-conductors havingintermediate conductive foils, and closing the envelope about the foilsby pinch sealing, pinch sealing being accomplished using pinch jawswhich are so shaped as to displace the foils and the adjacent envelopematerial laterally such that, in the finished lamp, the foils aredisplaced from a central longitudinal axis through the lamp whilst theconductors leading from the foils to the interior of the envelope extendparallel to the said axis. The pinch jaws may comprise a female jaw intowhich a male jaw can slide, the female jaw having a pinch face whichincludes a recess and the male jaw having a pinch face including aprojection, the recess and projection cooperating during pinching todisplace the foils and adjacent envelope material laterally.

Preferably, the pinch seal is formed with a ledge or shoulder in apredetermined location relative to one of the internal components of thelamp in order to provide a reference abutment facilitating accuratepositioning of the lamp capping and mounting structure with respect tothe internal components.

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is an exploded perspective view of a tungsten halogen automobileheadlamp bulb embodying the invention,

FIG. 2 is a side elevation of the bulb per se illustrating a pinch sealthereof,

FIG. 3 is another side elevation of the bulb, viewed at right angles tothe illustration of FIG. 2, the pinch seal being shown sectionally inthe process of being formed between a pair of pinch jaws, and

FIG. 4 is a cross-section through the finished pinch seal shown inposition between the pinch jaws.

The lamp 10 shown in FIG. 1 of the drawings is a tungsten-halogenautomobile headlamp bulb internationally known as the H4" type. The lamphas main and dippedbeam filaments l2 and 13 respectively. The dippedbeamfilament 13 is positioned in front of a miniature bowl reflector 14which is located, like the filaments 12, 13 within the lamp envelope 15.The envelope 15 is made of quartz and is hermetically sealed at thepoints l6, 17 to contain a halogen and a gaseous filling.

The filaments I2, 13 and reflector 14 are supported within the envelope15 by a sheet metal support having a plurality of individual fingers,generally indicated by 20. The support 20 is stiffened by an insulatingbridge 21, and its fingers are provided with individual conductors mostclearly seen in FIG. 1. Fabrication and assembly of the internalcomponents of the lamp l0, namely the filaments l2, l3, reflector 14,support 20 and insulating bridge 21, are disclosed in greater detail inour copending patent application Ser. No. 135,002, filed Apr. I9, 1971,now US. Pat. No. 3,774,064.

The individual conductors seen in FIG. 2 each include an inner conductorelement 23, in the form of either the end portion of the associatedfinger or a wire attached thereto. This element 23 is welded to one endof a molybdenum foil 24. The other end of the molybdenum foil is weldedto an outer conductor element or wire 25. The wire 25 in turn iselectrically connected to one of three input terminals 26 of a cappingstructure 27. The molybdenum foil is of the order of 0.00l0.002 inchesthickness and 2-4 mm. wide. The function of the molybdenum foil 24 is toenable a good hermetic seal 17 to be obtained between the envelope 15and the individual conductors. as is well known. The seal 17 is made bya pinching technique which will be described shortly.

The capping structure 27 includes a rectangular capping box 30 havingtwo sprung cars 31. The ears 31 serve to hold the box 30 firmly to thepinch seal 17 and to assist in centering the box 30 within an apertureof a cupshaped element 32. The box 30 has two inturned tangs 33 whichabut against a reference shoulder 34 of the pinch seal 27, formed duringthe pinch-sealing operation, and against the envelope at the point 35where the envelope swells outwardly from the pinch seal 17. Only onetang 33 is visible in the drawings. It will be appreciated that thepurpose of the two tangs 33 is to locate the box 30 correctly andpositively relative to the reference shoulder 34.

The element 32 is brazed or welded to the box 30 and its rim 35 isbrazed or welded to the inner wall of a cylindrical sleeve 38 formingthe body of the capping structure 27. A flanged element 39, commonlycalled a focussing collar, is then likewise secured to the sleeve 38.The sleeve 38 may be provided with locating lugs to fix the axialposition of the flanged element 39 relative to the sleeve 38. Theflanged element 39 is ap propriately shaped to enable the lamp to befitted and centered accurately in the receiving aperture of a standardvehicle headlamp reflector. The lower end of the sleeve 38 is closed byan insulating disc 40 bearing the terminals 26.

It will be recognised that the automobile lamp 10 must be veryaccurately made because its filaments 12, 13 have to be locatedprecisely relative to the optical axis and focal point of the associatedreflector. If the lamp 10 is inaccurately made, poor lightingperformance results. Furthermore, the filaments 12, 13 have to becarefully and precisely located relative to the wall of the envelope foran efficient halogen cycle to take place. Accurate manufacture of thecapping structure 27 has presented few problems, although in the pastdifficulty has arisen in locating the structure 27 axially relative tothe filaments 12, 13. The principal difficulty has been to ensure thatthe internal components of the lamp l0 retain their desired positions inthe envelope after pinch sealing.

It will be seen from the drawings that the conductor elements 23, arewelded to one face of the molybdenum foil 24. During pinch sealing, thefoil 24 presents a barrier resisting flow of the softened quartz. Thus,the foil 24 always remains central within the pinch seal. equalthicknesses of quartz being found in contact with the opposite faces ofthe foil 24 in the finished pinch seal. As a result, previous pinchsealing techniques have led to the conductor elements or wires 23, 25being subjected to bending movements such that they become off-centred.Correspondingly, the internal components carried by the element 23tended to depart from their designed positions within the envelope 15.Considerable lamp to lamp variations of the positions of the internalcomponents have been observed.

The pinch seal 17 according to this invention has a configuration whichensures that the conductor wires, particularly elements 23, retain theirdesired alignment relative to the central longitudinal axis of the lamp10 during and after pinch sealing. As a result, the three elements 23lie in a common plane containing the central longitudinal axis and allare parallel thereto.

The shape of the pinch seal 17 is most clearly seen in FIGS. 2 and 4 ofthe drawings. A central square or rectangular area 42 thereof, withinwhich the foils 24 lie, is displaced laterally relative to the remainderof the seal 17 and the said central longitudinal axis. The crosssectionof FIG. 4 shows this displacement most clearly. The displacement of area42 is such that the elements 23 are moved into coincidence with a plane43 which is to be understood to contain the said central longitudinalaxis. The single element 23 shown in FIG. 4 extends along this axis andlikewise lies in the plane 43. The molybdenum foils 24 are thus locatedto one side of the plane 43. The surfaces 44, 45 of the area 42 areequidistant from the surfaces of the foils 24 but are un equally spacedfrom the plane 43.

The remainder of the seal 17 consists of two longitudinally-extendingribs 47, 48 on either side of the area 42 and a transverse rib 50 at theend of the seal 17 furthest from the main body of the envelope 15. Theappearance of the area 42 is that of a projection on one side of theseal 17 and a corresponding depression between the ribs 47, 48 and 50 onthe other side of the seal.

The rib 50 defines the reference shoulder 34 previously mentioned.During manufacture, it is arranged that the distance between theshoulder 34 and, say, the adjacent end of the filament 13 is constantfrom lamp to lamp. By doing so, the axial location of the filamentsrelative to the capping structure 27, and particularly to the flangedelement 39, can be kept substantially con stant during lamp manufacture.

The pinch seal 17 is formed, after heating an end of the envelope 15 tosoften the quartz, by squeezing the quartz between a pair of pinch jaws51, 52 of interfitting male and female nature respectively.

The male pinch jaw 51 has an outstanding portion 53 having an end wall54, the configuration of which may be regarded as the negative of theside of the ultimate pinch seal 17 containing the above-mentioneddepression. Thus, the end wall 54 includes a central rectangu lar orsquare projection 55 for forming the said depression. Along either sideof the projection the end wall 54 is recessed to define shoulders 56 forforming the adjacent faces of the ribs 47, 48. The lower part of theprojection 55 is stepped to form a transverse surface 57 extendingacross the width of the male portion 53. The surface 57 is approximatelyequidistant from the faces of the shoulders 56 and the face of theprojection 55. The surface 57 is intended to form the transverse rib 50of the ultimate pinch seal 17.

The female pinch jaw 52 includes a cavity or groove 59 into which theportion 53 of the male jaw 51 can slide. The cavity or groove 59 is ofsubstantially U- shaped cross-section and its mouth is slightly taperedoutwardly to enable the male jaw 51 to slide into the cavity 59. Theinnermost wall 60 of the cavity 59 is of stepped configuration: thecentral part of the wall 60 being recessed to form the seal projectioncorresponding to the said rectangular or square depression.

In operation, the internal components of a lamp, together with theassociated conductors are held in a suitable jig and are then insertedinto a length of quartz tubing. The region of tubing which is to formthe eventual pinch seal is heated to soften the quartz and then thepinch jaws 51, 52 are closed upon the heated quartz. The jaws areadvanced until a seal as shown in FIG. 4 is produced. The jaws 51, 52may be stopped automatically by providing them with cooperating stoppingfaces, not shown. Alternatively, stopping faces can be incorporated inthe associated jaw carriers of a pinch sealing machine to preventexcessive pinching.

it will be recognised that the present invention is not limited to pinchsealing of automobile headlight bulbs. The invention can be appliedwherever it is desired to produce a lightbulb in which internalcomponents such as filaments have to be accurately located relative tothe envelope and seal region. The invention is thus of particular valuein the manufacture of precision lightbulbs for example of the pre-focustype.

The cup-shaped element 32 as described and illustrated adapts the sleeve38 of a conventional lamp cap, used for lamps having moulded glassseals, to fit the capping box 30. As an alternative, parts 32, and 38are made an integral construction which includes a hollow cylindricalportion and an end wall. The end wall is apertured appropriately toreceive the capping box 30 and has flanges, e.g. two in number, forengagement by the surface of the capping box 30. The flanges preferablyextend into the hollow interior of the cylindrical portion. The cappingbox 30 is welded or brazed to the said end wall. The alternativeconstruction is applicable not only to vehicle headlamp bulbs but to anylamp, including a prefocus lamp, where it is desired to fit a basestructure to a pinch seal. The use of such an alternative constructionin fabricating a lamp base is advantageous on the grounds of accuracy,ease of manufacture and economy.

We claim: 1. An electric lamp comprising: an envelope, support meanswithin said envelope, a filament carried by said support means, saidsupport means including means for electrically connecting said filamentto an external supply,

said connecting means comprising: at least two inner conductors, twoexternally-accessible outer conductors and a separate conductive foiljoining each of said inner conductors to an outer conductor,

said envelope having at least one pinch seal for sealing the envelope tosaid foils so that each of said foils is embedded in a pinch seal andequal thicknesses of envelope material are in contact with the oppositesurfaces of each of said foils,

a portion of said pinch seal within at least one of which said foils isembedded being displaced laterally with respect to the remainder of saidseal, and

each of said inner conductors leading into the interior of said envelopefrom its associated foil in a direction parallel to a centrallongitudinal axis through said lamp, said foils being laterallydisplaced from said axis.

2. A lamp according to claim 1, wherein said envelope has a single pinchseal into which each of said inner and outer conductors protrude, saidportion of said seal containing said embedded foils having a projectionon one face and a depression in its opposite face.

3. A lamp according to claim 1, further including seal capping and lampmounting means attached to said envelope said envelope having a shoulderproviding a reference abutment for said capping and mounting means, andsaid shoulder being at a predetermined location relative to a givenpoint inside said envelope.

4. A lamp according to claim 3, wherein said capping and mounting meanscomprises: a capping box in abutment with said shoulder, a sleeveencasing said capping box, and a focussing collar secured to saidsleeve.

5. A lamp according to claim 1, having a further filament carried bysaid supporting means, said supporting means including at least threeinner and outer conductors and interconnecting foils.

6. A lamp according to claim 5, wherein said inner conductors enter asingle pinch seal and all lie in a common plane containing said centrallongitudinal axis.

7. A lamp according to claim 5, further including a reflector carried bythe supporting means.

8. A lamp according to claim 1, further including a second filament,both said filaments being made of tungsten, said envelope being quartzand containing a halogen gas, and said support means carrying areflector adjacent one of said filaments, one end of each of saidfilaments being connected to a first inner conductor, and the other endsof said filaments being respectively connected to second and third innerconductors, said first, second and third inner conductors beingconnected through associated molybdenum foils to associated outerconductors, said foils being embedded in a common pinch seal, and saidinner conductors lying adjacent one another in a common plane containingsaid central longitudinal axis, said foils lying in a displaced planeparallel to said axis.

9. A lamp according to claim 8, wherein said common pinch seal has areference shoulder on one face thereof and futher including seal cappingand lamp mounting means embracing said seal, said seal capping and lampmounting means having means abutting said shoulder and a portion of saidenvelope adjacent said seal.

i i t l

1. An electric lamp comprising: an envelope, support means within saidenvelope, a filament carried by said support means, said support meansincluding means for electrically connecting said filament to an externalsupply, said connecting means comprising: at least two inner conductors,two externally-accessible outer conductors and a separate conductivefoil joining each of said inner conductors to an outer conductor, saidenvelope having at least one pinch seal for sealing the envelope to saidfoils so that each of said foils is embedded in a pinch seal and equalthicknesses of envelope material are in contact with the oppositesurfaces of each of said foils, a portion of said pinch seal within atleast one of which said foils is embedded being displaced laterally withrespect to the remainder of said seal, and each of said inner conductorsleading into the interior of said envelope from its associated foil in adirection parallel to a central longitudinal axis through said lamp,said foils being laterally displaced from said axis.
 2. A lamp accordingto claim 1, wherein said envelope has a single pinch seal into whicheach of said inner and outer conductors protrude, said portion of saidseal containing said embedded foils having a projection on one face anda depression in its opposite face.
 3. A lamp according to claim 1,further including seal capping and lamp mounting means attached to saidenvelope said envelope having a shoulder providing a reference abutmentfor said capping and mounting means, and said shoulder being at apredetermined location relative to a given point inside said envelope.4. A lamp according to claim 3, wherein said capping and mounting meanscomprises: a capping box in abutment with said shoulder, a sleeveencasing said capping box, and a focussing collar secured to saidsleeve.
 5. A lamp according to claim 1, having a further filamentcarried by said supporting means, said supporting means including atleast three inner and outer conductors and interconnecting foils.
 6. Alamp according to claim 5, wherein said inner conductors enter a singlepinch seal and all lie in a common plane containing said centrallongitudinal axis.
 7. A lamp according to claim 5, further including areflector carried by the supporting means.
 8. A lamp according to claim1, further including a second filament, both said filaments being madeof tungsten, said envelope being quartz and containing a halogen gas,and said support means carrying a reflector adjacent one of saidfilaments, one end of each of said filaments being connected to a firstinner conductor, and the other ends of said filaments being respectivelyconnected to second and third inner conductors, said first, second andthird inner conductors being connected through associated molybdenumfoils to associated outer conductors, said foils being embedded in acommon pinch seal, and said inner conductors lying adjacent one anotherin a common plane containing said central longitudinal axis, said foilslying in a displaced plane parallel to said axis.
 9. A lamp according toclaim 8, wherein said common pinch seal has a reference shoulder on oneface thereof and futher including seal capping and lamp mounting meansembracing said seal, said seal capping and lamp mounting means havingmeans abutting said shoulder and a portion of said envelope adjacentsaid seal.